The present invention relates to an automatic welding apparatus. More specifically the present invention relates to an improved automatic welding apparatus wherein tracing of the welding point is automatically performed in accordance with a preset or predetermined data.
Generally, in welding the workpiece of complex shapes in three dimensions, as distinguished from a plane and simple welding operation, it is required that the degree of freedom of the movement involved in the automatic welding apparatus be increased. However, the conventional automatic welding apparatus has been constructed that, for example, the fixture for the workpiece is fixedly secured, while the position of the torch fixture is movably controlled, namely, most of degrees of freedom or freedom degrees have been given to either one of the two fixtures. Accordingly:
1. When all the necessary freedom degrees have been given to the torch fixture, the worst welding condition, namely, a so-called upward welding operation can not be avoided;
2. The structure of a fixture which provides all the necessary freedom degrees becomes extremely complex; and
3. In the welding apparatus adapted to control spatial positions of cylindrical coordinates or polar coordinates, programming is extremely difficult particularly in control of a so-called PTP (Point To Point) system, since a welding line of the workpiece is generally in three directions such as longitudinal, lateral and vertical directions. Also, to avoid the difficulties, an interpolating means must be provided in the control device, thus resulting in a complex control device.
On the other hand, the control device, particularly, a position control device which has been used so far is classified mainly as a PTP type (Point To Point) and a CP type (Continuous Path). The PTP type of position control device is simple in construction and lower in cost, but its operation is not continuous, while the CP type of position control device is continuous in its operation, but is complex in construction, difficult to operate, and impractical. For example, in controlling the movement of the welding torch, the welding torch stops at each of its specified points with the conventional PTP control device. Accordingly, if the specified points are increased in number to perform controlling as close to a curve as possible, stop points are increased in number, thus making the welding finish worse. Accordingly, it is desirable that the position control device of the PTP type is improved to make its operation more continuous.
Therefore, it is a primary object of the present invention to provide an automatic welding apparatus, which is simplified in its mechanical construction and in its control device, wherein the necessary degree of freedom is divided between a fixture for a workpiece and a fixture for a torch to control the mutual positional relationship of the workpiece and the torch so that the welding operation may be performed under a better attitude of workpiece and torch in terms of welding conditions.
It is another object of the present invention to provide an automatic welding apparatus including a position control device of a PTP type which is capable of continuously controlling the position of an object to be controlled.
Still other objects and features of the present invention will be more apparent from the following detailed description taken in conjunction with the drawings.